Carcinoid tumors are uncommon neuroendocrine neoplasms. Most patients with tumors not amenable to early surgical resection develop metastic disease for which there is no effective treatment. These patients also frequently suffer form the malligant carcinoid syndrome, characterized by symptoms resulting from the synthesis and release of a number of hormones, most notably serotonin. Efforts to develop selective and effective chotherapy have been hampered by the paucity of data on biochemical features of the tumor which could be exploited for specific approaches to chemotherapy, to agents which selectively image carcinoid tumors and to treatment of the carcinoid syndrome. The first objective of this proposal is to characterize biosynthesis of serotonin in human carcinoid tumors. This objective is possible because of the unique resources of resected carcinoid material available at this institution. The second objective is to utilize that pathway for development of novel tryptophan analogs designed to irreversible inhibit and covalently bind to aromatic-L-amino acid decarboxylase (an obligatory enzyme in serotonin synthesis) thus trapping analogs in the tumor, and when ultimately bearing radioisotopes of iodine, to image and to treat carcinoid tumors. Specific aims of the proposal include: 1) characterization of serotonin biosynthesis in excised human carcinoid tumors and surrounding normal tissue, 2) stereospecific syntheses of alpha-(S)-fluoromethyltryptophan and alpha-(S)-fluromethyl-5-hdroxy-tryptophan analogs and B-fluro tryptophan analogs bearing iodine at positions 2,7,4 or 6 of the indole nucleus, meant to inhibit the decarboxylase by mechanism- based, irreversible binding to the tumor enzyme, 3) in vitro evaluation of the analogs including decarboxylase inhibition, and in some cases, prior activation by the serotonin biosynthetic enzyme trypothan hydroxylase (enzymes obtained from characterized sources, from a carcinoid cell line and from human carcinoid tumors), and 4)in vivo evaluation of promising analgos to include preliminary murine toxicology and pharmacology studies, and localization in nude mice implanted with human carcinoid cells. In preliminary studies, we have developed methods to characterized tryptophan hydrpxylase and aromatic-L-amino acid decarodylase in carcindoid tumor and shown that the decarboxylase is present in 7/8 human carcinoid tumor samples, and that the hydroxylase is present in 8/8 tumor samples. We have also developed methods for enantiospecific synthesis of alpha-fluoromethyltryptophan and completed preparations of model alpha-(S)- and alpha-(R)- monofluoromethyltryptophan and alpha-(S)- and alpha-(R)-5-OH- monofluromethyltrypophan and characterized their interactions with tryptophan hydroxylase and aromatic-L-amino acid decarboxylase, including documentation that alpha-(S)-, but not alpha-(R)-5-OH tryptophan irreversibly inactivates the decarboxylase.